Hydraulic lash adjuster



J. E. ESHBAUGH HYDRAULIC LASH ADJUSTER June 11, 1940.

Filed Jan. 30. 1939 2 Sheets-Sheet 1 :inventor w@ G .mwy .5, 6., .0/

HwMVrMu June A11, 1940. J; E. EsHBAUGH HYDRAULIC LASH ADJUSTER FiledJan. 30, 1959 2 Sheets-Sheet m. W y e,

Patented June 11, 1940 Y UNITED STATES HYDRAULIC msn AnJUs'rEa Jesse E.Eshbsugh, mint, Mich., signor to den` l eral Motors l poration ofDelaware` Corporation, Detroit, Mich.,'a cor- Applicationfranuary 3o,1939, serial No. 253,582

s claims.y (ci. 12s-9u) This invention has to do with valve lash arl-Vjusters of the type in which there is `a cylinder containing a body ofliquid, usually oil, on which rests a piston which engages the valve orvalve 5 operating mechanism or positions some part inthe valve operatingtrain. In such construction 'a valved passage is usually provided forsupplying oil from a suitable reservoirr to the hydraulic chambersupporting the piston. Means is provided to yieldingly urge the pistonout of the cylinder. The uid system comprising the hydraulic chamber,reservoir and passage is sealed by means of a suitable diaphragm securedat one end of` the cylinder and at the other end to the piston. It willbe found most convenient to make this diaphragm of oil-resistant rubberor other suitable flexible material.

It will be found that where the 'type of lash adjuster above describedis `arranged in the train of valve 'operating mechanism and moves withthe valve, the diaphragm will be subject to considerable distortionduring operation by` theb movement of the supply fluid back and forthunder the influence of inertia.

4Animportant object of the present invention consists in Ihe provisionof oil or other uid on the other side of the diaphragm so as tocounterbalance the eifect of inertia on the liquid coniined in thecylinder. With this arrangement the forces' operating on the diaphragm`are v balancedv and it is relieved of any substantial strain, therebylengthening its life.

Other features of the invention will be pointed outfin the course of the'description in which:

Figure l is a section through a portion of the valve mechanism of anL-head internal combustion engine showing one form of the improved lashadjuster. Figure 2 is a section on line 2-2 of Figure l. Figure 3 is afragmentary sectional view showing a slight modification of theconstruction of Figure 2.

Figures 4., 5, 6 and '7- are views corresponding to Figure 2 showingfurther modifications` v20 indicates a poppet valvekof a conventionalinternal combustion engine held upon its seat by the usual coil spring22. 24 indicates a portion of the automobile cam shaft carrying cam 26which engages roller I4 of tappet 28 in which my improved lash adjusteris incorporated. This tappet reciprocates in guide 30. Oil is suppliedfrom the engine lubricating system to the guide 3B through aperture 32.Tappet 23 consists of cylinder I having an inner bore 34, an-intermediate bore 36 and an outer bore 38, of graduated diameters as shown.In the intermediate bore 36 is guided the piston 2 having centralpassage 4U, the lower end of which is closed by disk 4of oil-resistantrubber whichis secured to the l0 outer end of piston 2 by means oftension spring or band 6 surrounding the outer end of the bellows andholding it in a groove provided in the outer end of the vpiston asshown. The inner end of the bellows is clamped under a retainer 6, ,upreferably made of sheet metal, which is presstted into the outerbore 38of the piston'and on to a shoulder formed at the junction of the outerbore and the intermediate bore.

8 indicates a coil spring seated at one end on $0 the retainer Ii and atthe other end bearing against stamped ring 'I held in placev by a C-shaped washer 9 engaged in an annular groove formed in the extreme outerend of piston 2.

3 indicates a valve stem engaging member in B5 the form of a disk guidedin the outer bore 38. y and` held against Withdrawal by means' of splitring I3 snapped into groove 42 formed in the outer end of the bore 38.

In the manufacture of the device the cylinder I :o with'thepistonassembly in it is immersed in oil under vacuum so as to displacewith oil all the air in the assembly. Thereafter the outer end of thecentral passage 40 in the piston 2 is sealed by driving a suitable plug43 of soft metal or 35 other material into it and the diaphragm 4 issecured in place as described, thereafter disk 3 is inserted in thecylinder and split ring- I3 is snapped in position. I The unit is nowready for. insertion in the engine in the position indicated 40 inFigure 1 and during the operation of the engine acts as follows to takeup lash or clearance that maydevelop:

When the carn'26 engages the roller I4, moving the tappet cylinder Iupwardly, oil cannot get u; out of the hydraulic chamber below thepiston because valve' III is held closed not only by spring II but alsoby the much greater pressure exerted through the oil as the result ofthe upward movement of the cylinder. Consequently, the piston! is forcedupwardly and with it the valve engaging `member 3 and the valve 20.During the opening` are held in the described relation. After the u,

' ever any lash or clearance develops in the valve l valve reaches itsseat if any lash or clearance exists in the valve operating mechanism,spring 8 expands, pushing the tappet down against the cam I4 and pushingthe piston 2 and valve engaging member 3 upwardly against the valvestem. This increases `the volume of the hydraulic chamber vbeneath thepiston causing oil to be drawn down from vthe supply inside thediaphragm 4 through passages 45 and central passage 40 past the valve I0into -the hydraulic chamber. Such action occurs whenoperating mechanism.

At times it is necessary that the over-all length of the tappet shoulddecrease to enable the valve to rest on its seat when the roller I4 ison the base circle of the cam. This condition. occurs when the valve andtappet become heated during engine operation and expand. W'hen thisoccurs the valve spring 22 exerts pressure against.

the valve stem engaging mernr 3 and piston 2 not only during the valveopening and closing movements but also when the tappet engages the basecircle of' the cam. llhis heavy pressure causes increased leakage of oilvbetween piston 2 and cylinder I thereby allowing the piston to descendfurther into the cylinder permitting the valvel 20 to seat.

The above is a simplified statement of operation rather than a preciseone. It will be understood that there is always a certain amount ofleakage of oil between the `piston 2 and cylinder I vduring each valveoperating cycle and there is also, during each cycle a certain amount ofoil which passes through valve I into the hydraulic chamber. Anyadjustments of the piston 2 in the cylinder are eiected by a successionof very .small movements. Thus, increase inthe overall length of thetappet to take up lash is accomplished by a series of additions tothesupply of oil in the hydraulic'chamber in excess of the amount escapingbetween the piston and cylinlder.

shortening of the over-all length of the tappet is accomplished througha succession of valve operating cycles in which oil is forced outbetween the piston and cylinder and none is admitted owing to the factthat valve I0 is always held upon its seat by spring and the pressure onthe oil resulting from the failure of the engine valve to completelyclose. The described adjustments are taking place continuously duringthe operation ofthe engine and insure that the valve operating mechanismwill be continuously operating without substantial lash or clearance.

The described construction has the advantage that the hydraulic chamberand the oil supply for the chamber are sealed against the entrance ofdust and air, butv is open to the objectiony that the iiexible diaphragm4 is `subject to distortion as a result of surging of the oil. confinedwithin it by reason of its inertia. This objection I have overcome byvproviding a'body of oil within the outer bore 38 surrounding the diaphragm. This oil' comes from the engine lubricating system throughpassage 32. Groove A4i collects some of it'irom the tappet guide and itreaches the reservoir 49 in the interior of the tappet through suitablepassages 5|. The reservoir 49 fills with oil soon after the engine isput into service and remains lled. Any air that maynd its way into thereservoir escapes through hoe clearance between disk 3 and the tappetre. Figure 3 there is shown a slight modiiication 'ases-,95a

'ment `is such that groove |00 is always covered by a portion of theguide 30 throughout its stroke so that oil reaching the chamber 49 haslittle chance of escape and so is at all times in position tocounterbalance the pressure of the oil inside the .diaphragm In themodification shown in- Figure 4, tappet |02 provided atits lower endwith roller |04, has a central bore |06, receiving piston |08 having acentral recess H0 in one portion of which there is secured by force fita thimble ||2 on which is .spun a cage H4 housing spring IS and diskvalve H8. The upper end of the bore IIII is closed by plug after thedevice has been completely filled with oil. On the piston |06 thererests disk |22 guided for sliding movement in stamping |24 which is apress t in the enlarged portion of the recess in the upperpart of thetappet |02. Sealing gasket |26 is interposed between the stamping and a.shoulder in the cylinder |02. `|28 indicates a corrugated bellows whichis shown made of metal although it ,'may be made of .rubber as in theprevious form.

The upper end of this bellows is clamped between ring |30 secured to theupper end of the piston |08 and theheaded over portion |32 of the upperend of the p ton |08. The lower endof the diaphragml |20 is secured tothe inturned edge of the stamping |24. Coil spring |34 positioned withinthe diaphragmy as shown exerts yielding upward pressure` on the piston|08 through its engagement with the member |30.

With this construction the interior of the diaphragm Iza and the portionvof the bore of the cylinder |02 below it, including the passages in thetappet, are completely filled with oil before inserting the tapered plug|20. Oil is supplied to the exterior of the diaphragm |23Vthroughpassages |36 in the cylinder |02 and stampingl |24 as shown. Thepassages |36 communicate as before with an annular groove |38 in theouter surface of the cylinder |02. This groove is supplied withv oilfromthe engine lubricating system in the ways previously described.

vThis modiiication as well as those later to be described operates inthe same way .as the ,-preferred form. y

In the modiiication shown in Figure 5, tappet |40 provided with roller|42 is centrally bored to receive piston |44 urged outwardly of thecylinder by spring |46 bearing against apertured washer |40 on whichrests weaker spring |50 urging disk valve Ii2-against its seat which isformed on thimble |54 which is a press t in the central bore in thepiston |44. The bore in the piston communicates through passage with theinterior of the chamber formed by exible diaphragm |58, one end of whichis clampedbetween a shoulder inside the tappet |40 and a sleeve threadedto the body of the tappet. The upper, end of the diaphragm |58 issecured to a groove in the upper end of piston |44 by a wire or othersuitable clamping device |32. Disk |64 rests on the upper end ofthepiston |44.

An expanding split ring |30 is secured in a groove in the upper end ofthe bore of the tappet to limit the outward movement ofthe disk I 84.

Tappet |40 is grooved at |88 as shown and this groove communicates by,passages |10 with the chamber surrounding the diaphragm |58. Thisconstruction is very 'simple and has certain advantages in easeofmanufacture. l

In the form shown inFigure 6, tappet |12 reciprocating in guide |14is'bored out to receive piston |16 made in two parts,` the upper part|18 preferably being a press it in the. lower part. Spring |80 urgespiston |16 out of the body of the tappet, the part` |18 of the piston'isprovided with a central ybore |82 and an intersecting bore |84, thelower end of the part |18 provides a seat for disk valve |86 themovement of which is limited by screw |88 provided with lock nut |80,the

screw being threaded into the lower end of the piston |16. Passages |82connect the chamber belowA the piston with yond the valve |88.

clamped between the shoulder formed in` the bore of the tappet and aring |88 which is a press fit in the bore. The upper end of thediaphragm An advantage of the modication last described is theadjustable play oi.' the valve |86.v If desired, a small coil; springmay be provided* to yieldingly hold valve |88 on its seat.

Figure '1 shows a further modiiication in which the tappet 2|0 comprisesan outer cylinder 2|2 in which is tted or secured an inner cylinder 2|44in which is slidably guided the piston 2|6 yieldingly urged outwardly bycoil spring 2| 8. Disc valve 220 controls passages 222 which may be ofthe same construction as those shown in Figure 6, extending through theupper part 224 of the piston. Diaphragm 226 of a constructionsubstantially the same as that shown in Figures A and` 6 is secured atits lower end to the upper end 4of cylinder 2|4 and at its upper end tothe part 224 of the piston. The piston part 224 engages they end of thevalve stem indicated at 228.

In this form of the invention a felt washer 280 mounted in stamping 232fitted in the upper end of cylinder 2|0 engages the upper portion ofpiston part 224. j

'I'his device operates in substantially the same manner as thosepreviously described'except that the felt washer 230 permits oil to`slowly seep through into the chamber below thereby Providing fluidaround the outside of thediaphragm 226 to counterbalance the forceexerted on it by the oil within the diaphragm due to the rapid movementof the tappet. With this arrangement it is unnecessary to provide anyother means for the entrance oi' oillinto the interior of the tappet.v

Obviouslythis invention'is applicable to'hydraulic valve mechanism ofothertypeafor' exthe passages leading be- Diaphragm |84 which ispreferably of rubberis 3 ample, the typeshown in Almen Patent 1,936,653

in which the hydraulic dash pot serves to adjust the position of amember in the valve operating train but is not itseliv subjected to thefull valve operating pressure.

It will be noted that the bottom of the piston 2 is spaced but ashortdistance from the shoulder formed at the junction of the inner bore84 and the -intermediate bore 36 of the tappet. This is for thepurposeof making `it possible for the shoulder to engage the pistonandyoperate the valve even though there be no oil at all in the tappet.yoperated at all times even though the operation l be very noisy.

In the forms of the invention shown in Figures 5, 6 and 7 it will, ofcourse, be desirable to employ iilling plugs like plug 48 ot Figure 2and plug |20 of Figure 4 for convenience in initially filling thetappets with oil.

I claim: l

` 1. In a valve lash adjuster the combination of 'a cylinder, a pistonin the cylinder, means yield- `ingly urging the piston out oi' thecylinder, a

passage leading from the portion oi' the cylinder on one side of thepiston to the portion of the ,cylinder on the other side of the piston,a valve in said passage preventing the escape of oil from the bottom ofthe cylinder when pressure is applied thereto, a flexible diaphragmconnected to the piston at a point above said passage and to thecylinder, a body of oil sealed within the cylinder by the diaphragm, abody of oil in the cylinder surrounding the diaphragm, and means forconilning the last-named body of oil in said cylinder so as to preventsurging thereof while permitting a slight amount of leakage so thatentrained air may escape.

., v2.- In the combination as deiined in claim 1,

saidlast named `means including a valve stemengaging member slidablyguided in said cylinder and supported by said piston.`

3. In valve operating mechanism for internal combustion engines and thelike the combination of a valve, means for yieldingly holding the valveon its seat, and means for moving the valve from its seat comprising atappet in the form of a cylinder having one end closed, aguide for thetappet, a piston in the cylinder, means "for yieldingly urging thepiston out of the'cylin-der, a passage through the piston to admit oilto the hydraulic chamber formed between the piston and the bottom of thecylinder. a check valve in' said passage, a diaphragm connected to thepiston and the cylinder forming a vreservoir between it and the upperend of the piston, a body of oil lling This assures that the engine maybeV

